Suction collection device

ABSTRACT

A suction collection system particularly suitable for drawing fluids from a patient area and storing the fluids for later use or disposal, which is operable in any orientation of the device, thereby providing a field operable system which may be transported in battlefield conditions. The portable suction system consists of a cylindrical evacuating chamber with a top sealing cap. A suction port on the sealing cap is connected to the fluid collection bag, which consists of a laminar flexible plastic bag having an air permeable, liquid impermeable patch or portion through which air may pass for purposes of providing a vacuum suction, yet the collected fluids will remain in the bag. The suction power is provided by a vacuum pump which is electronically regulated by periodically energizing and de-energizing the pump to conserve power supply energy.

This is a continuation of co-pending application Ser. No. 660,472 filedon Oct. 12, 1984, abandoned.

DESCRIPTION TECHNICAL FIELD

This invention is in the field of suction apparatus and, moreparticularly, relates to suction apparatus for drawing fluids from apatient area and storing the fluid in a disposable receptacle.

BACKGROUND ART

Suction devices are used in many medical applications to draw variousfluids from the patient area and to store the fluids for later use ordisposal. Suction devices have been utilized to draw aspirated fluidsfrom a patient during a surgical operation and during the post-operativeperiod. Suction devices are also used to drain fluids from thegastrointestinal tract, as well as to drain pulmonary mucous in trachealincisions, and the like. Suction sources may be fixed or mobile. Thefixed systems comprise wall vacuum outlets connected to a centralsystem. The mobile systems are either relatively large capacity deviceswhich are bulky or portable systems. Portable suction sources operate onpower supplied by either electricity, compressed gas or manual power andmay be used in a hospital, ambulance, home, or in the field. A summaryof the state-of-the-art in portable suction devices is set forth inHealth Devices, March 1978, page 11 and pages 120-141.

In emergency conditions, such as in battlefield operations, it would beextremely desirable to have a portable suction device capable ofcontinuous operation in any orientation. The known prior art suctioncollection systems are incapable of operation if the collectioncontainer tips over and falls in a sideways or upside-down position.Additionally, most prior art portable suction devices are calibrated forvacuum levels at one location and must be recalibrated if operated atdifferent altitudes. Accordingly, a need exists for a relativelylightweight portable suction system capable of delivering regulatedsuction of precise vacuum and precise flow rate, which is capable ofcontinuous operation in any orientation of the system.

DISCLOSURE OF THE INVENTION

The present invention relates to a compact, lightweight, portablesuction system in which the vacuum for suction purposes is provided byevacuating a rigid plastic chamber or cannister having an end wall withan orifice connected to a vacuum pump and an open top sealed by asealing cap. A disposable bag having a patch of semi-porous material isaffixed to a suction port on the cap. The patch is made of hydrophobicmaterial which has a porosity such that it is permeable to air andimpermeable to fluids such as blood, as well as most bacterial matter.The suction port in the sealing cap, or cover, is fluidly connected to asuction tip. The collection bag is integrally attached to the sealingcap and this unit may be sterilized and handled as a disposable unit.Because the hydrophobic patch pores are impermeable to bacteria, thedisposable unit, once internally sterilized, remains asepticallyisolated from the outside environment.

In operation, the rigid chamber, or cannister, is evacuated by thevacuum pump, thus drawing air and fluids through the suction tip intothe suction port and into the flexible collection bag with thehydrophobic patch where the liquids are retained for collection. The airpasses through the semiporous material and through the orifice on theend wall of the chamber and into the vacuum pump where it is exhausted.A check valve is provided between the vacuum pump and the chamber toprevent backflow of air and to vent the vacuum pump to atmospherethrough a solenoid valve when the pump is off. In this manner, thenegative pressure in the vacuum pump is relieved so that when the pumpstarts again, it does so under no load conditions.

An electronic regulator maintains the required vacuum by cycling orperiodically energizing and de-energizing the vacuum pump. In apreferred embodiment, the device is battery powered. The use ofelectronic regulation of vacuum by cycling the pump instead ofconventional mechanical regulation, conserves battery power and extendsthe useful operating time between charges.

Additionally, the battery may be recharged by means of an externalcharger or via a photovoltaic array provided with the system. Ninepreset vacuum levels are provided by a simple switch mechanism. Inaddition the vacuum may be continuously varied over a wide range. Thevacuum level is displayed on a control panel meter. Continuous orintermittent vacuum may be selected from the control panel. The devicewill operate in any orientation.

Intermittent suction flow may be preselected for a period of time "On"and a different period of time "Off". The intermittent On and Offperiods may be varied by internal adjustments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a preferred embodiment of the inventionshowing the general electromechanical features thereof.

FIG. 1A is a section along lines 1A--1A of FIG. 1.

FIG. 2 is a top perspective view of the suction bag and integral sealingcap disposable unit of the suction system of the invention.

FIG. 2A is a partially exploded bottom perspective of the unit of FIG. 2with the suction bag folded back on itself.

FIG. 2B is a sectional view along lines 2B--2B of FIG. 2.

FIG. 3 is a side perspective view of the rigid container of theinvention.

FIG. 3A is a side view of the fluid stop tube 17.

FIG. 3B is a sectional view of the bottom portion of container 12 withstop tube 17 in place.

FIG. 4 is a side perspective view of the suction system housing showingthe vacuum pumps and other portions of the invention.

FIG. 5 is a top perspective view of the suction system showing thecontrol panel.

FIG. 6 is a detailed schematic drawing on two sheets of theelectro-mechanical portions of the preferred embodiment of FIG. 1.

FIG. 7 is a schematic view of an alternate embodiment of the invention.

FIG. 8 is a perspective view of a further embodiment of the disposableunit of the invention.

FIG. 9 is a perspective view of another embodiment of the disposableunit of the invention.

BEST MODE OF CARRYING OUT THE INVENTION GENERAL DESCRIPTION

Referring now to the block diagram of FIG. 1, an overall generaldescription of the suction system will be provided in connectiontherewith prior to a detailed description of specific items. As may beseen in FIG. 1, a suction tip 15 is connected by a fluid conduit 14 to asuction port 74 on a plastic sealing top cover 24. Conduit 14 is affixedto a nipple on the external side of suction port 74, such as bywell-known heat sealing means; or a press fit connection may be made.

The interior side of port 74 extending through the bottom of cap 24 iscoupled to an input port or opening on one side of flexible containerbag 10. Bag 10 is partially formed of hydrophobic material 11b which isimpervious to fluids such as blood yet permits air to pass through itspores. Bag 10 is affixed to port 74 in such a manner as to be readilyfolded about itself, as shown in FIG. 1A, so as to fit inside circularcontainer 12. This enables a large volume of liquid to be accumulated inthe bag which expands to almost fill the relatively small cylindricalcontainer. A continuous airway is formed by the vacuum sensor tube 20and a second small cap inlet 25 (See FIG. 2B) which extends throughcover 24 into chamber 12.

The cap 24, collector bag 10, port 74 and tube 20 form an integraldisposable unit which may be capped and sterilized and provided in anaseptic package for disposable usage. The inner periphery 24b of cap 24is adapted to form a vacuum tight fit with the outer cylindrical wall12a of chamber 12.

Chamber 12 is a rigid plastic light transparent cannister of cylindricalshape having an exterior wall surface 12a and a bottom wall 12b with aprojecting portion 12c to which is affixed on O-ring seal 22. Thecylindrical shape is preferred since it is desired to seal the top and acircular cover 24 over the circular opening forms a self-sealingstructure unlike other possible shapes. Chamber 12 is adapted to beremovably mounted on block 16 by inserting the projecting portion 12cinto a corresponding opening 16a in block 16 whereby the O-ring 22 formsa vacuum seal against opening 16a.

An orifice 19 is provided through projecting portion 12c. Orifice 19mates with conduit 13 extending through block 16. A fluid stop tube 17mates with orifice 19 to prevent flow of fluid into the system in theevent bag 10 should rupture.

Thus, when chamber 12 is mated with block 16 and bag 10 inserted inchamber 12 and sealing cap 24 covers the chamber, a complete airsuction/vacuum path is provided from tip 15 to conduit 13 in block 16.

Conduit 13 is coupled through access viewing tube 18 to check valve 26which in turn is coupled to the output port of vacuum pump 30 andsolenoid valve 34. Solenoid valve 34, which is operated by transistorswitch 36, vents vacuum pump 30 to atmosphere via port 33 during timeintervals when the pump is off for the purpose of removing negativepressure to allow the pump to re-start under no load conditions.

Suction is generated by vacuum pump 30 which is energized andde-energized by transistor 36. The vacuum may thus be electricallycontrolled by operation of transistor 36, as will be described below.

The vacuum in chamber 12 is sensed by vacuum transducer 44 via port 46which is coupled to tube 20 on cap 24. Vacuum transducer 44 convertsactual vacuum from chamber 12 to an analog voltage signal which iscoupled via lead 44a to one input terminal of voltage comparator 38. Theother input terminal of voltage comparator 38 is normally coupled to avacuum control voltage signal from rotary switch 42 via lead 42a.

If the control voltage signal differs from the vacuum voltage signal atthe input leads to the comparator 38 an output signal appears on lead38a which biases transistor switch 36 ON causing a current path to becompleted to ground through the solenoid of valve 34 and the motorwindings of vacuum pump 30 via lead 37 until such time as the voltagesat the input to comparator 38 are equalized in which case the vacuum inthe chamber is at the level commanded by the setting of switch 42.

The control voltage signal is set by the operator's selection of one ofmany positions of switch 42 which is tied to the center taps of aplurality of multi-ganged potentiometers 50 fed a reference voltageV_(A) by voltage regulator 58. In one position of switch 42, acontinuously variable potentiometer may be selected whereby the operatormay continuously vary the vacuum setting.

Voltage regulator 58 regulates the voltage V_(B) from the battery orother power supply used by the unit to provide a regulated referencevoltage V_(A) of 5.0 volts D.C. which is coupled to potentiometers 50and additionally through a resistor to an input lead of amplifier 39wherein the reference voltage may be summed with the vacuum voltagesignal from transducer 44 and the summed signal displayed on ammeter 41as a measure of the actual vacuum in chamber 12.

An intermittent circuit 40 comprising a transistor switch controlled bya multivibrator oscillator may be connected to the output lead 42a ofswitch 42 to periodically ground one of the inputs to comparator 38thereby periodically interrupting the operation of pump 30.

Disposable Unit

Referring now to FIGS. 2, 2A and 2B, the details of the disposablebag/cap unit will be explained. FIG. 2 is a top perspective view withthe bag 10 lying flat and the top external surfaces of sealing cap 24shown in detail. FIG. 2A is a bottom perspective view of the bag/capunit with bag 10 folded back on itself to show the details of thepressure sensor port 23. FIG. 2B is a section through lines 2B--2B ofFIG. 2.

Bag 10 consists of a first planar sheet 11a of polyethelene plastic. Theplastic sheet 22a on the side away from the viewer in FIG. 2. A secondplanar sheet 11b of semi-porous material is provided on the oppositeside. Sheet 11b is a laminate of porous polytetrafluoroethylene andpolyester fabric having a suitable pore size to enable passage of airbut prevent passage of liquid and/or most bacteria. Sheet 11b is heatsealed along its borders to a third sheet 11c of non-porous polyethelenecentrally cut out to conform to the outer border of semi-porous sheet11b. Sheet 11c is in turn heat sealed to the outer border of bottomsheet 11a; and forms an air and liquid impervious sealed frame aroundsemi-porous patch 11b. Air can pass through sheet 11b but not throughthe remaining bag surfaces and because of the porosity of sheet 11b,liquids such as blood will not pass through any of the bag surfaces. Thepore size for sheet 11b depends upon the surface tension which thematerial generates on the liquid and the desired breakthrough pressure.A pore size of 0.1 micron to 0.2 microns is suitable for apolytetrafluoroethylene/polyester laminate at breakthrough pressures of20 psi to 7 psi.

It is important to note that while bag 10 may be entirely fabricated ofhydrophobic material 11b, as shown in FIG. 9, the embodiment shownherein in FIGS. 2 and 2A is preferred for cost reasons since suchmaterial is much more expensive than the non-porous material 11a or 11c.It will be realized that since the bag and cap unit is intended to beprovided as a disposable unit, which is used once and then discarded,cost is an important factor.

However, as will be explained in detail in connection with FIG. 8, whenfabricating the bag 10 with porous and non-porous portions, it is vitalthat the porous portions be of adequate length and breadth relative tothe internal dimensions of the chamber and located such that whendisposed in the container 23, the porous portion is positioned so thatin any orientation of the container, a surface of the porous materialwill not be covered by collected liquid until the desired liquid levelis reached. Otherwise, suction will be lost in when the porous portionis completely covered by liquid.

Thus, in the preferred embodiment shown herein, the bag 10 is configuredwith respect to the inner diameter of container 12 so that in order toinsert the bag into the container, the bag must be folded into agenerally cylindrical shape with the porous patch on the exterior, asshown in FIGS. 1 and 1A. Also, the patch extends in height and widthalong substantially the entire surface of one side of bag 10.

An inlet opening 500 is provided in sheet 11 on the porous patch 11b.The bag 10 is affixed to inlet port 74 by centering opening 500 on theport opening 74a and gluing or heat sealing a portion of sheet 11 aboutthe periphery of the opening 500 to a planar flange portion 74b of port74. This method of affixing bag 10 to cap 24 enables one to form alow-cost planar bag using current machinery. The precise location ofopening 500, either on the porous patch or non-porous surfaces, is notcritical since the bag is operable in any position. Port 74 extendsthrough an oval opening 24e in a planar top surface 24c of cap 24 fromwhich external reinforcing ribs 24d extend externally in a plane normalto surface 24c. An inner sealing surface 24b of cap 24 extendsdownwardly from the top surface 24c about the circular periphery of cap24.

A nipple portion 74c of port 74 extends outwardly from cap surface 24cthrough the oval opening in 24e in cap surface 24c. A cylindrical wall24f extends from opening 24e to bottom surface 74b of port 74. Bottomsurface 74b intersects the plane of cylindrical wall 24f at an angleforming a circular opening 74a at the base of port 24. An optional cover25 for the nipple portion 74c of port 74 is provided with the disposableunit. Cover 25 forms a press fit over the nipple portion of port 24 and,of course, is removed prior to operation of the unit.

As shown in FIG. 2b, pressure sensor tube 20 extends into a circularopening 23a formed at one end of cylindrical tube 23 integral with cup24. Tube 20 is affixed at the bottom to a nipple 25 having an opening 31at the bottom wall 23a of tube 23. A disk 29 of porous plastic materialis affixed by adhesive or heat bonding to the bottom of tube 23 coveringopening 31.

Disk 29 is preferably formed of porous polyethelene, a material havingpores of sufficient porosity to be permeable to air but which clog whencontacted by fluids. A suitable pore size is in the order of 20 microns.The function of disk 29 is therefore to prevent backflow of fluid frombag 10 into vacuum transducer 44 (FIG. 1) which is connected to chamber12 via tube 20. Such backflow may occur if bag 10 should break withfluid in it during pump operation.

Chamber

The details of chamber 12 are shown more clearly in FIGS. 3, 3A,and 3B.Chamber 12 is formed of rigid plastic material such as polycarbonate andhas an outer cylindrical wall 12a, an end wall 12b, and an open topadapted to be sealed by cap 24 (previously mentioned in connection withFIG. 2).

A tubular orifice 19 extends through a projecting portion 12c of endwall 12b. Orifice 19 extends along the length of fluid stop tube 17until terminated at top wall 17a of tube 17.

Tube 17 is formed of the same porous polyethelene material as disk 29and performs a similar function. In the event bag 10 ruptures for anyreason while within chamber 12, any fluids within bag 10 will beprevented from passing through orifice 19 since the fluids will clog upthe pores of tube 17.

Fluid stop tube 17 is removably mounted to bottom wall 12b of chamber 12by an O-ring seal 502 within an annular groove 21 on tube 17. Projection12c with corresponding O-ring 22 is used to removably affix chamber 12to wall 16a (FIG. 4) of base block 16.

Packaging

Referring now to FIG. 4, the packaging of the suction system of theinvention may be shown in detail. The electronic control circuitry isprovided on a panel 450 which may slide into carrying case 400 on rails452 and 453. The vacuum pumps 30A and 30B are located below the controlpanel. Exhaust ports 80 and 82 are provided to decrease the noise of thepumps. Batteries 64A and 64B are stored below the pump and the D.C.charger supply 58 is located below the batteries.

The instrument panel is shown in FIG. 5 to comprise an ammeter 41 fordisplaying vacuum levels, a rotary switch 42 for selecting vacuumlevels, battery level LED 48, power switch 41 and spring illuminatingswitch 60. The panel is recessed within a protective covering plate 72.Handle 70 is provided at the top of the carrying case.

Electromechanical System

The details of the electromechanical portions of the invention will beexplained in connection with the schematic of FIG. 6. Like numeralreferences with other figures are utilized in FIG. 6.

Starting with the voltage supply 64 it may be seen that two 6-voltbatteries 601 and 602 are connected in series from ground, or thenegative side, through 3 amp circuit breaker 604 to spring return switch60. When switch 60 is in the normally on (N.O.) position about 14 voltsis applied to two illuminating lamps 48A and 48B on the control panel.Battery 601 is coupled in series through circuit breaker 603 to arm 605Aof power switch 605. In the ON position, switch arm 605A provides 14volts to D.C. regulator 58a. A solar cell 606 is connected in parallelwith the two batteries between ground and the anode side of diode 607.Diode 607 provides unidirectional current from solar cell 606 tocontinuously charge batteries 601 and 602 and to prevent reverse currentflow to the solar cell.

A battery charging circuit may be supplied from a conventional A.C.transformer adapter (not shown) coupled across input jacks 701 and 703.Alternatively, if a battery supply having a voltage between 14 and 40volts D.C. is available, it may be coupled across jacks 702 and 703 tosupply internal battery charging current. This voltage is regulated downto the correct voltage for charging the two batteries by voltageregulator 900. Diodes 704, 705 and 706 protect the regulator 900 fromreverse current flow. Adjustable potentiometer 709, in series connectionwith resistor 708, is used to adjust the charging voltage to the correctlevel. Capacitor 710 is a filter used to reduce noise ripple effects.

The voltage from voltage supply 64 is coupled through arm 605A of powerswitch 605 to D.C. regulator 58a. D.C. regulator 58 is a commerciallyavailable regulator made by National Semiconductor Company, ModelLM2931. Regulator 900 (previously mentioned) is a Model LM317K,available from the same source. The regulated output voltage from D.C.regulator 58 is labelled V_(A) and is supplied throughout the schematicat various terminals, also labelled V_(A). The unregulated D.C. voltageV_(D), provided at the input to regulator 58 is coupled via lead 720 tovoltage test circuit 80 (sheet 2) and a number of other placesthroughout the schematic, which are also labelled V_(D).

Regulated voltage V_(A) is coupled to one side of 9 potentiometers,labelled VR1, VR9, in potentiometer assembly 50. The center tap of eachpotentiometer is coupled to separate terminals a-i on rotary switch 42.The potentiometer resistors are coupled together in parallel andgrounded on one side, thus various voltages, depending on the positionof the center tap of each potentiometer may be coupled to the terminals42a-i of 10 position rotary non-shorting switch 42.

An additional 100,000 ohm single turn potentiometer VR10 is coupled inparallel with the other potentiometer to terminal j of rotary selectorswitch 42. One side of this potentiometer, VR10, is coupled through1,000 ohm resistor R3 to the regulated voltage supply 58 and the otherside of VR10 is coupled to ground. Thus, any one of the nine pre-setvoltages from potentiometers VR1-VR9, may be coupled through selectorswitch 42 to the input side of comparator 38 for setting the vacuumlevel in the chamber 12. Alternatively, the vacuum level may becontinuously varied by potentiometer VR10 in the "j" position ofselector switch 42. As will be explained, the vacuum level may bevaried, in this fashion, from 0 to 250 centimeters of water. The outputof rotary selector switch 42 is coupled through lead 715, as previouslymentioned, to the + input of voltage comparator 38 (See sheet 2), whereit provides a control voltage for setting the vacuum.

The minus terminal of voltage comparator 38 is coupled via lead 716 tothe output lead of vacuum transducer 44. Vacuum transducer 44 may be acommercially available device, such as a 142PC05DL manufactured byMicroswitch Company, a division of Honeywell Company. Vacuum transducer44, as previously mentioned, is coupled via port 46 to vacuum sensorport 20 so as to sense the differential vacuum (or negative pressure)within chamber 12 with respect to atmospheric pressure sensed by port45. The vacuum transducer 44 generates an electrical voltage signalproportional to the instantaneous value of the differential vacuum. Thissignal is compared in voltage comparator 38 with the control voltage vialead 715 from selector switch 42.

An output electrical signal is provided from comparator 38 as an inputto the gate terminal, G, of a field effect (FET) transistor switch 36.The source terminals of FET switch 36 is coupled to ground and the drainterminal D of switch 36 is coupled to the anodes of suppressor diodes720 and also to one side of the solenoid coil 34a and one side of thewindings of the motor of pumps 30. Pumps 30 are dual vacuum pumpspowered by a brushless D.C. motor (not shown).

Thus, in normal operation, a voltage difference between the two inputsignals to comparator 38 means that the negative pressure in chamber 12differs from the desired setting of potentiometers 50. A voltage outputsignal is generated by comparator 38 in response to this voltagedifference and this voltage output signal biases FET 36 ON to complete acurrent path from the 6 volt battery supply at 605B labelled V_(c) toground through the solenoid 34a of the solenoid valve 34 and the motorwindings (not shown) of vacuum pump(s) 30. The pump(s) 30 are therebyenergized. At the same time, current through the solenoid closes valve34 (FIG. 1) blocking the fluid vent path 32 to port 33 and atmosphericpressure.

Pump 30 continues to run until the negative pressure in container 12attains the level indicated by the potentiometer 50 settings, at whichtime, the voltage difference between the two input signals to comparator38 is nulled and no output biasing voltage will be coupled to the gateterminal of FET 36 causing the FET to stop conducting. This opens thecircuit path to ground from V_(c) through the pump 30 motor windings,thereby automatically stopping the pump motor(s) 30 when the correctvacuum level is reached. The circuit path from V_(c) through thesolenoid coil 34a is also opened and the solenoid valve is de-energizedto vent the pump 30 to atmosphere to remove the load on the pump when itis started again.

In the intermittent mode of operation which further conserves batterycurrent, switch 41 is placed in the intermittent position, thusconnecting the terminals labelled XB (sheet 2) and XA (sheet 1)together. This connection provides a coupling path for the intermittentcircuit 40 to short-circuit the control voltage, on lead 715, to groundat intervals of time determined by the intermittent circuit 40.Intermittent circuit 40, as may be seen, consists of a multivibrator 725in which the Off-time and On-time of the multivibrator are independentlycontrolled by the setting of the Off-time potentiometer R5 and theOn-time potentiometer R6.

Multivibrator 725 may comprise a commercially available multivibrator,such as an NE555. Resistor R6 is a 1 megohm resistor which is coupledthrough diode D1 to an input lead of multivibrator 725.

A battery test circuit 80 is provided wherein one-half of theunregulated battery voltage Vd on line 720 is coupled to the + side ofvoltage comparator 800. The other - side of voltage comparator 800 isprovided with regulated voltage from D.C. regulator 58 at the terminalmarked V_(A) through multiturn trimpot potentiometer R800. The settingof potentiometer R800 establishes the low point of suitable operatingbattery voltage.

When the battery voltage is above the low battery voltage setting, theoutput of the comparator 800 is high and the green LED 54 isilluminated. When the output of comparator 800 is high, transistor 804is biased to conduct, which holds multivibrator 806 in the reset mode.Multivibrator 806 is an oscillator. When it is held in a reset mode, itsoutput is held low. Therefore, the red LED 52 coupled to its output is"Off". When the battery voltage drops below the low point determined bythe setting of potentiometer R800, it is sensed by comparator 800 andthe comparator goes "low". The green LED 54 goes "Off". Transistor 804stops conducting. The reset voltage level to multivibrator 806 goes highand the multivibrator is no longer in the reset mode. The multivibratornow oscillates and turns the red LED "On" and "Off". Note: The green andred LEDS 52 and 54 are combined into one single package and to the userappear to be a single light. Vacuum level is displayed on meter 41. Thevacuum signal from transducer 44 is summed with zero adjust pot 21 withamplifier 39. Potentiometer 23 provides "full scale" gain adjustment.Alternately, battery voltage is displayed on meter 41 when spring returnswitch 65 is activated. Potentiometer 22 scales battery voltage VB toamplifier 39's gain setting. Meter 41 is a 0-100 μa meter and resistor24 converts the output voltage of amplifier 39 into the correct currentfor the proper meter operation.

It is important to note that the vacuum transducer 44 is a differentialdevice. It has one port 45 that is coupled to atmospheric pressure and asecond port 46 which is coupled to the interior of vacuum chamber 12.So, the device 44 is continuously comparing the vacuum chamber negativepressure against atmospheric pressure and providing a voltage signalproportional to the difference between the two. Thus, the calibration ofthe device is not affected by changes in atmospheric pressure whichmight come about from either changes in the weather or, moreimportantly, changes in altitude during use.

Portability, and hence weight, of the apparatus is an importantconsideration for the environment in which the suction collection systemmay be utilized. It is therefore desirable to minimize the weight of thebatteries and to maximize the running time of the pumps. In aconventional vacuum pump suction system, the pump runs continuously. Amechanical regulator limits the amount of maximum negative pressuredeveloped at the suction tip. The mechanical regulator is a diaphragmdevice biased by a spring which opens a passageway that allows outsideair to enter into the pump. The pump is constantly running at fullcapacity while the mechanical regulator limits the maximum amount ofnegative pressure that is available at the suction tip.

In the present device, the actual vacuum in the chamber is sensed andthe pump turned "on" and "off" electronically. The dead volume of thepump is very small, relative to the volume of the collection chamber andthe tubing so the duty cycle of the pump can be regulated to maintainvery precise levels of vacuum. Turning the pump "on" and "off" has thebattery conservation advantage of not requiring power when the pump is"off". In low suction flow conditions, such as chest drainageapplications, where a maximum of about 50 to 100 mls per minute flow isrequired, the amount of suction required is very small. So, to maintaina negative pressure of 30 or 40 centimeters, the pump needs to be "on"only a very small percentage of the time.

Another important advantage of the system above described, is theability to dial in any desired maximum negative pressure and have thepump operate to that instantly when the system is turned "on". With amechanical regulator, there is no absolute calibration. Instead, thesuction tubing is occluded and a mechanical gauge is read andadjustments made to the regulator until the desired pressure is reached.In the present device, it is only necessary to set one potentiometer tothe desired vacuum level, which is displayed on meter 41, turn on thedevice and that is the instantaneous maximum negative pressure.

An alternate embodiment of the suction collection system will now bedescribed in connection with FIG. 7, wherein parts similar to thoseshown in FIG. 1 will contain a like numeral designation and modifiedparts will carry a like designation with a prime suffix. The container12 of FIG. 7, while not shown in detail, is in all respectssubstantially the same as the container, as shown in previous figures.Bag 10' is a fluid collection bag having a air permeable, liquidimpermeable portion 11b and an impermeable sheet 11a similar to theconstruction shown in FIG. 1. However, in the embodiment of FIG. 7', bag10' is not formed integral with the cover cap 24'. Instead, a plasticnipple 700 is affixed to an opening at the top of bag 10', such as byheat-sealing or other suitable adhesion techniques.

Nipple 700 may then be suitably attached to fluid coupling port 74'which is, in turn, affixed to the top of cap 24'. Conduit 14 is alsoaffixed to the external end of port 74' and a suction tip 15 attached tothe remaining end of fluid coupling conduit 14. In all other respects,the cap 24' may be similar to cap 24 shown in FIG. 1, including thevacuum sensing port tubing 20, which is coupled to the vacuumtransducer.

The bag embodiment of FIG. 7 has the advantage of lower costmanufacture. However, there are certain disadvantages connected with theproblem of providing an aseptic port 74' if the cap is intended to bereused, as would be the intent in going to the embodiment shown in FIG.7. There are also disadvantages associated with the ability to providean adequate seal between the bag 10' and the nipple portion 700. Thesedisadvantages make the embodiment shown in FIG. 1 and previouslydescribed, more preferable at the present time.

FIGS. 8 and 9 show alternative embodiments of the invention in which thedimensions of the porous portion 11b are varied. In all other respects,the bags are similar to that shown in FIG. 2, described previously. Thebag 10" in FIG. 8 is affixed to the cap 24 in the manner previouslydescribed and is intended to form an integral disposable unit which maybe sterilized and disposed of after use. The embodiment of FIG. 8differs from that of FIG. 2 in that the porous portion 11b' is formed ina generally H-shaped configuration thereby utilizing less porousmaterial and therefore resulting in a lower cost disposable bag. TheH-shaped embodiment still retains sufficient length and breadth whenfolded about itself and disposed in a cylindrical container, such that aportion of the porous material will always be exposed above fluidcollected in the bag in any orientation of the chamber up to the desiredvertical height of collection desired.

In the embodiment of FIG. 9, the entire embodiment of 10'" is made ofporous material 11"b and is otherwise identical to and intended to besecured to cap 24 in the manner shown in connection with FIGS. 2 and 2a.This embodiment has the advantage of simplicity and ease in manufactureand may be preferred in those applications where the cost of the porousmaterial is not significant with respect to the intended usage.

We claim:
 1. A suction system comprising:(a) a rigid chamber with firstand second openings into the interior thereof, said first chamberopening adapted to be coupled to a suction tube; (b) a flexiblecollection bag having a portion of air-permeable, liquid impermeablematerial, said portion being of sufficient length in two dimensions,relative to the internal dimensions of the chamber, that when insertedinto said chamber it will have a surface area exposed above apredetermined liquid collection level in the bag for providing an airpermeable, liquid impermeable communication path between the interior ofsaid bag and the interior of said chamber in any orientation of thechamber, and a liquid inlet opening on said bag coupled to said firstchamber opening for providing a liquid permeable communication pathbetween the interior of said bag and said first chamber opening; (c) avacuum pump for evacuating said chamber; (d) fluid coupling means forproviding an air communication path between the second chamber openingand the vacuum pump.
 2. The system of claim 1 including a vacuum sensorand a third opening on said chamber coupled to said vacuum sensor andwherein said third opening on said chamber is coupled to said vacuumsensor which produces electrical signals proportional to the sensedvacuum and means for energizing and de-energizing said pump in responseto said electrical signals.
 3. The system of claim 1 wherein the chamberis generally cylindrical in shape and the flexible bag is dimensioned sothat for proper insertion into the chamber it must be folded back uponitself and, in that position, a section of the portion of material isexposed asbove a fluid collection volume in any chamber orientation. 4.The system of claim 1 wherein the bag is comprised of two elongateplanar surfaces and the portion occupies a majority of each of saidsurfaces, except at the periphery of the bag.
 5. The system of claim 3wherein the bag is comprised of two sheets joined at the peripherythereof.
 6. The system of claim 1 wherein the bag is formedsubstantially of said material.
 7. A suction system comprising:(a) arigid chamber with an orifice, and a sealable opening; (b) a sealingcover for said opening, said cover having a suction port; (c) a flexiblecollection bag adapted to be disposed within said chamber in operation;at least a portion of a surface of which comprises air-permeable, liquidimpermeable material and said bag having an opening coupled to one sideof said suction port; (d) a vacuum pump having a motor with windings,said pump being coupled to said orifice for establishing a vacuum insaid chamber; and (e) a vacuum sensing conduit extending through saidcover into said chamber and coupled to a vacuum transducer forgenerating signals to control the vacuum in said chamber by energizingand de-energizing said pump; and f. a solenoid valve electricallycoupled in parallel with said motor windings for venting said pump toatmosphere during time intervals when the pump is de-energized to allowthe pump to start under no load conditions.
 8. The system of claim 3including a control signal and wherein said vacuum transducer is coupledto said vacuum sensing conduit for converting negative pressure sensedby said transducer into an electrical signal which is compared with saidcontrol signal for setting the vacuum in said chamber by energizing andde-energizing said pump depending upon whether more vacuum or lessvacuum is respectively required.
 9. The system of claim 3 including atransistor switch, a battery for powering said pump and valve, and meansfor establishing a pre-set vacuum level and wherein the pump motorwindings and solenoid valve winding are coupled in parallel between D.C.voltage from said battery and ground through a transistor switch, theconductivity of said switch being controlled by the difference betweenthe vacuum sensed by said transducer and a pre-set vacuum level.
 10. Asuction system comprising:(a) a rigid chamber having a cylindrical sidewall, a bottom wall with an extended portion having a sealing member andan orifice extending into said chamber, and an open top; (b) a circularsealing cover for said open top, said cover having a suction port and avacuum sensing port; (c) a flexible collection bag adapted to bedissposed within said chamber in operation; a portion of the surface ofwhich comprises air-permeable, liquid impermeable material and having aninput port coupled to one side of said suction port; (d) a suction tipcoupled to another side of said suction port; (e) a battery; (f) avacuum pump powered by said battery coupled to said orifice forestablishing a vacuum in said chamber; (g) a vacuum sensing transducercoupled to said vacuum sensing port for providing signals proportionalto the vacuum in said chamber to periodically cycle said pump tomaintain a pre-set vacuum in the chamber thereby conserving batterypower and extending the useful operating time between changes of saidbattery.
 11. The system of claim 10 wherein said transducer is adifferential device having two ports, one of which is coupled toatmosphere and the other to said vacuum sensing port and wherein thesignals provided by said transducer are proportional to the differencebetween atmospheric pressure and the vacuum in the chamber.
 12. Asuction system comprising:(a) a rigid chamber having an end wall sectionwith an orifice and an open wall section; (b) a sealing cover for saidopen wall section, said cover having a suction port with a nippleportion and a vacuum sensing port; (c) a flexible collection bag havinga patch portion of air-permeabIe, liquid impermeable material and aninput port on said bag coupled to one side of said suction port; (d) asuction tube coupled to the nipple portion of said suction port; (e) abattery power vacuum pump for evacuating said chamber; (f) fluidcoupling means for providing a fluid path between the orifice on the endwall section of the chamber and the vacuum pump; (g) a check valve inthe fluid path for preventing reversal of fluid flow through said fluidpath; (h) a battery source of power for said vacuum pump; (i) atransducer coupled to said vacuum sensing port for providing a signal toenergize and de-energize the power to said pump in response to thedifference between the vacuum in the chamber and a pre-set vacuum level.13. The system of claim 12 wherein the vacuum pump includes a motorhaving motor windings; a solenoid having a solenoid winding in parallelwith said motor winding; a transistor switch in series between saidwindings and said battery source of power and ground; the conductivitystate of said transistor being controlled by said signal such that whensaid transistor is conducting, the motor is operable and the solenoid isoperable to vent said pump to the atmosphere, thereby enabling the pumpto operate under no load conditions.
 14. The system of claim 12 whereinsaid transducer is a differential device having two ports, one of whichis coupled to atmosphere and the other to said vacuum sensing port andwherein the signal provided by said transducer is proportional to thedifference between atmospheric pressure and the vacuum in the chamber.